1. Field of the Invention
The invention pertains to a torsional vibration damper, especially for a motor vehicle body.
2. Description of the Related Art
U.S. Pat. No. 6,082,507, which represents the basic type of device in question, describes a torsional vibration damper comprising:
a vane-equipped stator and a vaned rotor, where the stator and the rotor form at least two working chambers filled with damping medium, which chambers change their volume in opposite directions during the oscillating movement; and
at least one damping device, which is connected to at least one of the working chambers, where the working chamber connected to the damping device has at least one flow connection leading to the damping device, where the damping device has a collecting space, which is connected via the flow connections to each of the working chambers, the collecting space being divided in two, where each of the collecting spaces connects all of the working chambers of one rotational direction, the two individual collecting spaces being separated by a partition, in which the damping device is installed, where at least one of the collecting spaces is in working connection with a pre-pressurized compensating space.
In this type of vibration damper, the compensating space must be pre-pressurized in such a way that, for one rotational direction of the rotor, the maximum achievable damping pressure is lower than the pre-pressurization, because otherwise the separating piston would be pushed against the gas cushion in the compensating space. For this reason, a comparatively high level of pre-pressurization in the compensating space is chosen. This results in a high overall pressure level within the torsional vibration damper, as a result of which increased frictional forces occur between the rotor and the stator. It is already pointed out in U.S. Pat. No. 6,082,507 that the collecting space at the lower pressure level should be in working connection with the compensating space; nevertheless, the task still remains of lowering the level of the pre-pressurization in the compensating space below that present according to the state of the art.